This disclosure is generally directed to layered imaging members, photoreceptors, photoconductors, and the like that can be selected for a number of systems, such as copiers and printers, especially xerographic copiers and printers. More specifically, the present disclosure is directed to multilayered drum, or flexible, belt imaging members or devices comprised of a supporting medium like a substrate; an optional ground plane layer; an optional hole blocking layer; a photogenerating layer; and a charge transport layer, including at least one or a plurality of charge transport layers, and wherein at least one charge transport layer is, for example, from 1 to about 7, from 1 to about 3, and one; and more specifically, a first charge transport layer and a second charge transport layer, and where a polyalkylene glycol benzoate, such as a polypropylene glycol dibenzoate, and yet more specifically, a hydrophobic polypropylene glycol dibenzoate is incorporated in the charge transport layer, especially in embodiments where the polyalkylene glycol benzoate is present in the top charge transport layer, or in a first pass charge transport layer that is in contact with the photogenerating layer. The polyalkylene glycol benzoates are, in embodiments, substantially nontoxic and environmentally safe, and the charge transport of the photoconductors thereof possesses excellent wear characteristics.
The photoconductors disclosed herein possess a number of advantages, such as, in embodiments, the elimination of an anticurl backing coating layer (ACBC layer), minimal wearing of the charge transport layer or layers, and such as, for example, a reduced amount of wear from 25 nm/kcycle for a polytetrafluoroethylene containing charge transport layer to only a wear rate of 1 nm/kcycle for the polypropylene glycol, especially when present at 20 weight percent, containing charge transport layer, and a photoconductor lifespan of 1.4 million xerographic imaging cycles where there is imparted a flatness, such as for example from 150 to 180 degrees flat, orientation to the photoconductor. In addition, it is believed that further advantages of the photoconductors disclosed herein may enable the minimization or substantial elimination of undesirable ghosting on developed images, such as xerographic images, including decreased ghosting at various relative humidities; excellent cyclic and stable electrical properties; minimal charge deficient spots (CDS); compatibility with the photogenerating and charge transport resin binders; and acceptable lateral charge migration (LCM) characteristics, such as for example, excellent LCM resistance.
As the photoconductor belt bends and flexes over each belt support module during a xerographic machine function, the resulting internal strain facilitates early onset of fatigue and cracking causing premature photoconductor belt failure. Moreover, the presence of an ACBC layer not only increases the photoconductor production costs, it also adds total photoconductor thickness which can cause an increase in the photoconductor belt bending strain and increases fatigue and cracking.
Ghosting refers, for example, to when a photoconductor is selectively exposed to positive charges in a number of xerographic print engines, and where some of the positive charges enter the photoconductor and manifest themselves as a latent image in subsequent printing cycles. This print defect can cause a change in the lightness of the half tones, and is commonly referred to as a “ghost” that is generated in the previous printing cycle. An example of a source of the positive charges is the stream of positive ions emitted from the transfer corotron. Since the paper sheets are situated between the transfer corotron and the photoconductor, the photoconductor is shielded from the positive ions from the paper sheets. In the areas between the paper sheets, the photoconductor is exposed, thus in this paper free zone the positive charges may enter the photoconductor. As a result, these charges cause a print defect or ghost in a half tone print if one switches to a larger paper format that covers the previous paper print free zone.
Excellent cyclic stability of the photoconductor refers, for example, to almost no or minimal change in a generated known photoinduced discharge curve (PIDC), especially no or minimal residual potential cycle up after a number of charge/discharge cycles of the photoconductor, for example about 100 kilocycles, or xerographic prints of, for example, from about 80 to about 100 kiloprints. Excellent color print stability refers, for example, to substantially no or minimal change in solid area density, especially in 60 percent halftone prints, and no or minimal random color variability from print to print after a number of xerographic prints, for example 50 kiloprints.
Also included within the scope of the present disclosure are methods of imaging and printing with the photoconductors illustrated herein. These methods generally involve the formation of an electrostatic latent image on the imaging member, followed by developing the image with a toner composition comprised, for example, of thermoplastic resin, colorant, such as pigment, charge additive, and surface additive, reference U.S. Pat. Nos. 4,560,635; 4,298,697 and 4,338,390, the disclosures of which are totally incorporated herein by reference, subsequently transferring the toner image to a suitable image receiving substrate, and permanently affixing the image thereto. In those environments wherein the photoconductor is to be used in a printing mode, the imaging method involves the same operation with the exception that exposure can be accomplished with a laser device or image bar. More specifically, the flexible photoconductor belts disclosed herein can be selected for the Xerox Corporation iGEN® machines that generate with some versions over 100 copies per minute. Processes of imaging, especially xerographic imaging and printing, including digital and/or color printing, are thus encompassed by the present disclosure, and where the photoconductors are, in embodiments, sensitive in the wavelength region of, for example, from about 400 to about 900 nanometers, and in particular from about 650 to about 850 nanometers, thus diode lasers can be selected as the light source. Moreover, the imaging members of this disclosure are useful in color xerographic applications, particularly high-speed color copying and printing processes.